Vehicle gaseous fuel supply system

ABSTRACT

A vehicle gaseous fuel supply system includes a high pressure filter, a primary pressure-reducing valve, a solenoid cut-off valve, safety means, and a secondary pressure-reducing valve. A regulator is formed by disposing the high pressure filter, the solenoid cut-off valve, and the primary pressure-reducing valve on a common regulator body that has a passage providing a connection between the high pressure filter and the solenoid cut-off valve, a passage providing a connection between the solenoid cut-off valve and the primary pressure-reducing valve, and an exit passage having one end connected to the primary pressure-reducing valve. Between the safety means and the secondary pressure-reducing valve which are connected to the other end of the exit passage, at least the secondary pressure-reducing valve has its valve housing formed as a body separate from the regulator body. As a result, the dimensions of the regulator formed by integrating a plurality of components can be reduced thereby lessening restrictions on the layout, and the arrangement of passages in the regulator body can be simplified thereby making the machining easy and achieving a reduction in cost.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vehicle gaseous fuel supply systemthat includes a high pressure filter that removes impurities from highpressure gaseous fuel supplied from a tank, a primary pressure-reducingvalve that reduces the pressure of the gaseous fuel from whichimpurities have been removed by the high pressure filter, a solenoidcut-off valve disposed between the high pressure filter and the primarypressure-reducing valve, safety means that operates in response to theoutput pressure of the primary pressure-reducing valve exceeding a setpressure, and a secondary pressure-reducing valve that further reducesthe pressure of the gaseous fuel whose pressure has been reduced by theprimary pressure-reducing valve and supplies it to an injector of anengine.

2. Description of the Related Art

Conventionally, such a system is already known in, for example, JapanesePatent Application Laid-open No. 11-270718, wherein a filter, a solenoidcut-off valve, a primary pressure-reducing valve, a relief valve, and asecondary pressure-reducing valve are integrated on a common regulatorbody, thereby forming a regulator.

In the above-mentioned conventional arrangement, since a high pressuresection up to the primary pressure-reducing valve and a low pressuresection after the primary pressure-reducing valve are integrated on thecommon regulator body, the regulator body must be made of a materialthat is compatible with the high pressure section. The material of theregulator body therefore has a greater strength than is required forparts related to the low pressure section, and there is further room forcost reduction. Furthermore, since a large number of components areintegrated on the regulator body, the arrangement of passages in theregulator body becomes complicated, and the machining applied to theregulator body becomes correspondingly more difficult. Moreover, thedimensions of the regulator body increase, thus causing restrictions onthe layout relative to other components when the regulator is mounted ona vehicle.

SUMMARY OF THE INVENTION

The present invention has been carried out in view of theabove-mentioned circumstances, and it is an object of the presentinvention to provide a vehicle gaseous fuel supply system that reducesthe dimensions of a regulator in which a plurality of components areintegrated, thereby lessening restrictions on the layout, and simplifiesthe arrangement of passages in a regulator body, thereby making themachining easy and achieving a reduction in cost.

In order to accomplish the above-mentioned object, in accordance with afirst aspect of the present invention, there is proposed a vehiclegaseous fuel supply system that includes a high pressure filter thatremoves impurities from a high pressure gaseous fuel supplied from atank, a primary pressure-reducing valve that reduces the pressure of thegaseous fuel from which impurities have been removed by the highpressure filter, a solenoid cut-off valve disposed between the highpressure filter and the primary pressure-reducing valve, safety meansthat operates in response to the output pressure of the primarypressure-reducing valve becoming equal to or exceeding a set pressure,and a secondary pressure-reducing valve that further reduces thepressure of the gaseous fuel whose pressure has been reduced by theprimary pressure-reducing valve and supplies it to an injector of anengine, wherein the high pressure filter, the solenoid cut-off valve,and the primary pressure-reducing valve are disposed on a commonregulator body to form a regulator, the regulator body having a passageproviding a connection between the high pressure filter and the solenoidcut-off valve, a passage providing a connection between the solenoidcut-off valve and the primary pressure-reducing valve, and an exitpassage having one end connected to the primary pressure-reducing valve,and wherein, between the safety means and the secondarypressure-reducing valve which are connected to the other end of the exitpassage, at least the secondary pressure-reducing valve has a valvehousing formed as a body separate from the regulator body.

In accordance with the above-mentioned arrangement of the first aspect,among the high pressure filter, the solenoid cut-off valve, the primarypressure-reducing valve, the safety means, and the secondarypressure-reducing valve, the high pressure filter, the solenoid cut-offvalve, and the primary pressure-reducing valve which are on the highpressure side are integrated on the regulator body to form theregulator, the arrangement of the passages in the regulator body issimplified in comparison with the conventional regulator formed byintegrating the whole of the high pressure section and the low pressuresection, and the machining of the regulator body becomes correspondinglyeasier. Moreover, the regulator can be made compact, and when it ismounted on a vehicle, restrictions on the layout relative to othercomponents can be lessened. Furthermore, since the valve housing of atleast the secondary pressure-reducing valve between the safety means andthe secondary pressure-reducing valve which are on the low pressureside, is formed as a body separate from the regulator body, the valvehousing of the secondary pressure-reducing valve can be formed from amaterial having a comparatively low strength, thereby achieving areduction in cost.

Furthermore, in accordance with a second aspect of the presentinvention, in addition to the first aspect, there is proposed a vehiclegaseous fuel supply system wherein a mounting face for providing saidother end of the exit passage with an opening provided on the outer faceof the regulator body, and bodies each having a low pressure passage andequipped with safety means of different types operating in response tothe pressure of the low pressure passage are selectively mounted in adetachable manner on the mounting face so that the low pressure passagecommunicates with said other end of the exit passage. In accordance withthe above-mentioned arrangement, one of the plural types of safety meanscan be selectively connected to the regulator, thereby enhancing themulti-purpose feature when the gaseous fuel supply system is mounted ona vehicle.

Furthermore, in accordance with a third aspect of the present invention,in addition to the above-mentioned arrangement of the second aspect,there is proposed a vehicle gaseous fuel supply system wherein theplural types of safety means are a pressure switch that determines thecut-off timing of the solenoid cut-off valve and a relief valve. Inaccordance with the above-mentioned arrangement, it is possible tofreely select preventing a high pressure equal to or exceeding the setpressure from being applied to the secondary pressure-reducing valve byactivating the solenoid cut-off valve so that it closes when the outputpressure of the primary pressure-reducing valve becomes equal to orexceeds the set pressure; or preventing a high pressure equal to orexceeding the set pressure from being applied to the secondarypressure-reducing valve by releasing a part of the gaseous fuel outputfrom the primary pressure-reducing valve when the output pressure of theprimary pressure-reducing valve becomes equal to or exceeds the setpressure.

The above-mentioned object, other objects, characteristics andadvantages of the present invention will become apparent fromexplanations of preferred embodiments that will be described in detailbelow by reference to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 22 illustrate a first embodiment of the present invention.

FIG. 1 is a schematic diagram showing the arrangement of a gaseous fuelsupply system.

FIG. 2 is a plan view showing a state in which the gaseous fuel supplysystem is mounted on a vehicle.

FIG. 3 is a side view of a regulator.

FIG. 4 is a top view of the regulator from arrow 4 in FIG. 3.

FIG. 5 is a bottom view of the regulator from arrow 5 in FIG. 3.

FIG. 6 is a cross section at line 6—6 in FIG. 4.

FIG. 7 is a cross section at line 7—7 in FIG. 3.

FIG. 8 is a magnified longitudinal section of a solenoid cut-off valve.

FIG. 9 is a magnified longitudinal section of a primarypressure-reducing valve.

FIG. 10 is a top view of a leaf spring provided in the primarypressure-reducing valve.

FIG. 11 is a cross section at line 11—11 in FIG. 10.

FIG. 12 is a side view of a secondary pressure-reducing valve from arrow12 in FIG. 13.

FIG. 13 is a view from arrow 13 in FIG. 12.

FIG. 14 is a view from arrow 14 in FIG. 13.

FIG. 15 is a cross section at line 15—15 in FIG. 14.

FIG. 16 is a cross section at line 16—16 in FIG. 13.

FIG. 17 is a magnified view of an essential part in FIG. 16.

FIG. 18 is a top view of a partition provided in the secondarypressure-reducing valve.

FIG. 19 is a cross section at line 19—19 in FIG. 18.

FIG. 20 is a magnified longitudinal section of a diaphragm provided inthe secondary pressure-reducing valve.

FIG. 21 is a top view of a leaf spring provided in the secondarypressure-reducing valve.

FIG. 22 is a cross section at line 22—22 in FIG. 21.

FIGS. 23 and 24 illustrate a second embodiment of the present invention.

FIG. 23 is a cross section corresponding to FIG. 6 of the secondembodiment.

FIG. 24 is a cross section corresponding to FIG. 23 in a state with analternative body.

DESCRIPTION OF PREFERRED EMBODIMENTS

The first embodiment of the present invention is explained below byreference to FIGS. 1 to 22. Referring to FIG. 1, compressed natural gas(hereinafter called CNG), which is a gaseous fuel, is stored in one or aplurality of CNG tanks 20 at high pressure, for example, 25 to 1 MPa.The CNG tanks 20 are equipped with corresponding container cut-offvalves 21 that are connected in common both to a filling inlet 22 via acheck valve 23, and to a manual cut-off valve 24. A pressure sensor 26and a temperature sensor 27 are attached to a pipeline 25 between thecontainer cut-off valves 21 and the manual cut-off valve 24.

When the container cut-off valves 21 and the manual cut-off valve 24 areopen, CNG from the CNG tanks 20 is guided to a regulator RA via a highpressure pipeline 28 equipped with an oil filter 29 for removing oilthat might have contaminated the CNG when the CNG tanks 20 were filledwith CNG by a compressor. The pressure of the CNG is reduced to, forexample, 0.6 to 0.7 MPa in the regulator RA, and the CNG is then guidedto a secondary pressure-reducing valve 31 via a low pressure filter 30.The pressure of the CNG is reduced to, for example, 0.2 to 0.3 MPa inthe secondary pressure-reducing valve 31, and the CNG is then guided toan injector 32 of an engine E via a pipeline 33 provided with atemperature sensor 34 and a pressure sensor 35.

In FIG. 2, within the engine compartment of a vehicle V, the engine E,which is a multicylinder engine, has a plurality of injectors 32, whichare connected in common to a gaseous fuel pipeline 36. The secondarypressure-reducing valve 31 placed in the vicinity of the engine E isconnected to the gaseous fuel pipeline 36 via the pipeline 33. The lowpressure filter 30 connected to the secondary pressure-reducing valve 31is also placed in the vicinity of the engine E. In order to minimize thelength of the high pressure pipeline 28, which guides the CNG from theCNG tanks 20 mounted on a rear part of the vehicle V, the regulator RAis separated from the engine E and placed in a rear part of the enginecompartment.

The regulator RA is formed by providing a high pressure filter 39, asolenoid cut-off valve 40, and a primary pressure-reducing valve 41 on acommon regulator body 38A having a hot water passage 37. The regulatorRA is also provided with a pressure switch 42 as safety means.

The high pressure filter 39 removes impurities present in the CNG guidedfrom the manual cut-off valve 24 via the high pressure pipeline 28. Theprimary pressure-reducing valve 41 operates so as to reduce to, forexample, 0.6 to 0.7 MPa the pressure of the CNG at a high pressure of 25to 1 MPa that has passed through the high pressure filter 39 to removeimpurities. The solenoid cut-off valve 40 is provided between the highpressure filter 39 and the primary pressure-reducing valve 41 and closeswhen the engine E stops operating or in response to a signal output fromthe pressure switch 42. Furthermore, the pressure switch 42 changes itsswitching mode, for example, when the pressure of the CNG whose pressurehas been reduced by the primary pressure-reducing valve 41 becomes equalto or exceeds a predetermined set pressure, for example, 1.65 MPa, andoutputs a signal to close the solenoid cut-off valve 40.

Engine cooling water is introduced from the engine E to the hot waterpassage 37 of the regulator body 38A so that the temperature of theregulator body 38A does not drop excessively due to the reduction inpressure in the primary pressure-reducing valve 41. In addition, athermostat 43 positioned separately from the regulator body 38A controlsthe temperature of the regulator body 38A and prevents it from risingexcessively by closing a valve when the temperature of the enginecooling water circulating in the hot water passage 37 exceeds, forexample, 70° C.

Referring to FIGS. 3 to 7 together, the regulator body 38A is formed soas to have a transverse cross section with a substantially rectangularshape. The high pressure filter 39 is mounted on the regulator body 38Afrom, among its outer side faces, a first side face 44 side, the firstside face 44 being formed so as to protrude outward slightly. Thesolenoid cut-off valve 40 is mounted on the regulator body 38A on asecond side face 45 that is opposite the first side face 44. A recess isprovided on a third side face 46 among the outer side faces of theregulator body 38A, the third side face 46 providing a connectionbetween the first and second side faces 44 and 45. The recess is used asthe hot water passage 37. A cover plate 47 is fastened to the third sideface 46 so as to cover the recess and is fitted with a pair ofconnecting pipes 48 and 49 for supplying the engine cooling water to anddischarging it from the hot water passage 37.

The regulator body 38A has a first end face 50 and a second end face 51that is opposite the first end face 50, the end faces beingperpendicular to the first to third side faces 44 to 46. The primarypressure-reducing valve 41 is mounted on the regulator body 38A on thefirst end face 50 side. The pressure switch 42 is mounted on aprojection 51 a provided on the regulator body 38A so as to project outof the second end face 51.

The arrangements of the high pressure filter 39, the solenoid cut-offvalve 40 and the primary pressure-reducing valve 41 forming theregulator RA are explained below in order.

(High Pressure Filter 39)

Referring in particular to FIG. 7, a recess 53 is provided in the firstside face 44 of the regulator body 38A. A pipe fitting 54 is screwedinto the aperture at the outer end of the recess 53 so that an annularseal 55 is interposed between the inner end of the pipe fitting 54 andthe regulator body 38A. The high pressure pipeline 28 guiding CNG fromthe manual cut-off valve 24 is connected to the outer end of the pipefitting 54. The high pressure filter 39 is fitted in the recess 53 so asto leave a gap between the higher pressure filter 39 and the inner endof the pipe fitting 54. Disposed between the high pressure filter 39 andthe pipe fitting 54 is a spring 56 exerting a resilient force thatpresses the high pressure filter 39 against the closed inner end of therecess 53.

Formed between the regulator body 38A and the outer periphery of thehigh pressure filter 39 fitted in the recess 53 is an annular unpurifiedchamber 57 communicating with the interior of the pipe fitting 54.Provided in the regulator body 38A is a passage 59 communicating with apurified chamber 58 within the high pressure filter 39. CNG guided viathe high pressure pipeline 28 thus flows from the unpurified chamber 57into the purified chamber 58 while passing through the high pressurefilter 39, and the CNG from which impurities have been removed is guidedto the passage 59.

(Solenoid Cut-off Valve 40)

Referring also to FIG. 8, the solenoid cut-off valve 40 is mounted onthe second side face 45 of the regulator body 38A at a position oppositethe high pressure filter 39.

The solenoid cut-off valve 40 includes a coil assembly 60, a guide tube61 made of a non-magnetic material, a fixed core 62 fixedly attached tothe guide tube 61 so as to block one end thereof, a plunger 63 slidablyfitted within the guide tube 61 so as to face the fixed core 62, areturn spring 64 disposed between the fixed core 62 and the plunger 63,a solenoid housing 65 made of a magnetic metal, a magnetic support frame66 screwed into the regulator body 38A so that the coil assembly 60 isinterposed between the magnetic support frame 66 and the solenoidhousing 65, and a valve member 67 retained by the plunger 63 on the sideopposite the fixed core 62. One end of the guide tube 61 is insertedinto the coil assembly 60 and the other end is fixed to the regulatorbody 38A. The solenoid housing 65 is fastened to the fixed core 62 so asto cover the coil assembly 60.

The coil assembly 60 is formed by covering a bobbin 68 made of asynthetic resin and a coil 69 wrapped around the bobbin 68 with a cover70 made of a synthetic resin. Provided integrally with a part of thecover 70 on the regulator body 38A side so as to project outward is acoupler 70 a, a pair of connector terminals 71 connected to the coil 69extending to the coupler 70 a. Leads (not illustrated) are connected tothe coupler 70 a.

Provided on the second side face 45 of the regulator body 38A are asmall-diameter hole 73 with its inner end closed and a large-diameterhole 74 having a larger diameter than that of the small-diameter hole 73and coaxially connected to the outer end of the small-diameter hole 73,with an annular step 75 disposed therebetween, the step 75 facingoutward. One end of the guide tube 61 is inserted into the bobbin 68 anda collar 61 a is provided integrally on the outer face of the other endof the guide tube 61 so that the collar 61 a protrudes outward in theradial direction and its outer periphery is adjacent to the inner faceof the large-diameter hole 74. Said other end of the guide tube 61 isinserted into the large-diameter hole 74 with an annular seal 76interposed between the collar 61 a and the step 75.

The magnetic support frame 66 is mounted on the regulator body 38A byscrewing it into the large-diameter hole 74. Moreover, the seal 76 andthe collar 61 a are interposed between the step 75 and the magneticsupport frame 66, thereby fixing the guide tube 61 also to the regulatorbody 38A.

A threaded shaft 62 a is integrally provided so as to be connected tothe fixed core 62 while penetrating the central part of the closed endof the solenoid housing 65, which has a bottomed cylindrical form. A capnut 78 is screwed around a part of the threaded shaft 62 a projectingout of the solenoid housing 65 with a washer 77 disposed between thesolenoid housing 65 and the cap nut 78. Tightening the cap nut 78fastens the central part of the closed end of the solenoid housing 65 tothe fixed core 62.

Said other end of the guide tube 61 is fixed to the regulator body 38Aand is inserted into the large-diameter hole 74. Slidably fitting theplunger 63 in the guide tube 61 forms a main valve chamber 79 betweenthe inner end of the small-diameter hole 73 provided in the regulatorbody 38A and said other ends of the guide tube 61 and the plunger 63.Moreover, the passage 59 communicating with the purified chamber 58 ofthe high pressure filter 39 communicates with the main valve chamber 79,and CNG from which impurities have been removed by the high pressurefilter 39 is introduced into the main valve chamber 79.

A passage 80 is provided in the regulator body 38A so as to open in thecentral part of the inner end of the small-diameter hole 73. An annularvalve seat 81 is provided on the regulator body 38A so as to surroundthe open end of the passage 80 in the main valve chamber 79, the valveseat 81 projecting slightly toward the main valve chamber 79 side.

The valve member 67 is formed by integrally providing a pilot valve part67 a on one end side and a main valve part 67 b on the other end sidevia a connecting tube 67 c that forms steps between the two valve parts67 a and 67 b. The pilot valve 67 a is formed in a disc shape having onone end a tapered face whose diameter decreases toward the plunger 63side. The main valve part 67 b is formed in a disc shape that faces theinner end of the small-diameter hole 73. The diameter of the pilot valvepart 67 a is set so as to be smaller than the diameter of the main valvepart 67 b. Provided coaxially on the central part of the valve member 67are a first passage 82 that communicates at all times with the passage80 and a second passage 83 communicating with the first passage 82 andopening on the central part of said one end face of the pilot valve part67 a, the diameter of the second passage 83 being smaller than that ofthe first passage 82.

The end of the plunger 63 facing the main valve chamber 79 is providedwith a recess 84, into which the pilot valve part 67 is inserted. Thepilot valve part 67 a is loosely inserted into the recess 84 andprevented from becoming detached from the recess 84 by a C-shapedstopper 85 fixed to the other end of the plunger 63. Formed between thepilot valve part 67 a and the plunger 63 is a pilot valve chamber 86communicating with the main valve chamber 79. A rubber seal 87 isembedded in the central part of the closed end of the recess 84. Therubber seal 87 blocks the aperture of the second passage 83 in the pilotvalve chamber 86 when the central part of said one end of the pilotvalve part 67 a is seated. The stopper 85 is therefore fixed to theplunger 63 at a position where the pilot valve part 67 a can moveaxially relative to the plunger 63 between the closed end of the recess84 and the stopper 85.

Embedded in the face of the main valve part 67 b facing the closed endof the small-diameter hole 73 is an annular rubber seal 88 that blockscommunication between the main valve chamber 79 and the passage 80 bysitting on the valve seat 81.

In such a solenoid cut-off valve 40, cutting the power supply to thecoil 60 makes the plunger 63 move in a direction away from the fixedcore 62 due to the spring force of the return spring 64, the rubber seal88 of the main valve part 67 b is seated on the valve seat 81, blockingcommunication between the main valve chamber 79 and the passage 80, andthe pilot valve part 67 a is seated on the rubber seal 87, blockingcommunication between the pilot valve chamber 86 and the passage 80,thereby suspending supply of high pressure CNG to the passage 80 side.

On the other hand, supplying power to the coil 60 first makes theplunger 63 move sufficiently to the fixed core 62 side to detach thepilot valve part 67 a from the rubber seal 87, and the second passage 83communicating with the passage 80 via the first passage 82 therebycommunicates with the pilot valve chamber 86. As a result, CNG graduallyflows from the main valve chamber 79 to the passage 80 via the pilotvalve chamber 86, the second passage 83 and the first passage 82, andthe difference in pressures applied to the main valve part 67 b from themain valve chamber 79 side and from the passage 80 side becomes small.When the electromagnetic force due to the coil 60 overcomes the pressuredifference acting on the main valve part 67 b, the plunger 63 movesfurther toward the fixed core 62 side, the rubber seal 88 of the mainvalve part 67 b departs from the valve seat 81, and CNG thereby flowsfrom the main valve chamber 79 to the passage 80.

(Primary Pressure-reducing Valve 41)

Referring also to FIG. 9, a valve housing 90 of the primarypressure-reducing valve 41 is formed from a part of the regulator body38A on the first end face 50 side and a cover 91 fastened to the firstend face 50 of the regulator body 38A by a plurality of bolts 92. Theperiphery of a diaphragm 93 is interposed between the first end face 50of the regulator body 38A and the cover 91 having a cylindrical part 91a.

A pressure-reducing chamber 94 is formed between a recess 95 provided onthe first end face 50 and the diaphragm 93. The regulator body 38A isprovided with a mounting hole 97 extending toward the second end face 51side, one end of the mounting hole 97 opening in the central part of thepressure-reducing chamber 94. The mounting hole 97 is formed from afirst hole part 97 a, a second hole part 97 b having a smaller diameterthan that of the first hole part 97 a, a third hole part 97 c having asmaller diameter than that of the second hole part 97 b, and a fourthhole part 97 d having a smaller diameter than that of the third holepart 97 c. One end of the first hole part 97 a opens at the central partof the closed end of the recess 95. One end of the second hole part 97 bis coaxially connected to the other end of the first hole part 97 a. Oneend of the third hole part 97 c is coaxially connected to the other endof the second hole part 97 b. One end of the fourth hole part 97 d iscoaxially connected to the other end of the third hole part 97 c. Thepassage 80 for guiding CNG from the solenoid cut-off valve 40 opens onthe inner face of the second hole part 97 b.

A cylindrical valve seat member 98 is screwed into the first hole part97 a of the mounting hole 97 so that an annular seal 99 is interposedbetween the valve seat member 98 and the step formed between the firstand second hole parts 97 a and 97 b. That is to say, a female thread 100is cut into the inner face at one end of the first hole part 97 a in themounting hole 97, and the valve seat member 98 is screwed into thefemale thread 100.

Projectingly provided on the end face of the valve seat member 98 on thepressure-reducing chamber 94 side are a plurality of, for example, fourprojections 102 forming a plurality of, for example, four channels 101extending in the radial direction of the valve seat member 98 in a planeperpendicular to the axis of the mounting hole 97. These channels 101are arranged in a cross shape. When the valve seat member 98 is screwedinto the female thread 100, the valve seat member 98 can therefore berotated by engaging a tool (not illustrated) with the channels 101arranged in the cross shape. The valve seat member 98 can thus be easilyfitted into the regulator body 38A.

Formed between the valve seat member 98 and the step formed between thesecond and third hole parts 97 b and 97 c in the mounting hole 97 is avalve chamber 103 communicating with the passage 80. The valve seatmember 98 is integrally provided, at the end on the pressure-reducingchamber 94 side, with an inward collar 98 a protruding inward in theradial direction. A valve hole 104 communicating with thepressure-reducing chamber 94 is formed on the inner periphery of theinward collar 98 a. Formed on the inner face of the inward collar 98 ais a tapered valve seat 105 facing the valve chamber 103 with the valvehole 104 opening in the central part of the valve seat 105.

Housed within the valve chamber 103 is a valve body 106 made of asynthetic resin, the valve body 106 being able to be seated on the valveseat 105 and being fixed to a valve stem 107 placed coaxially with thevalve hole 104.

The valve body 106 is formed in a cylindrical shape having a tapered endfacing the tapered valve seat 105 so that the valve body 106 can beseated on the valve seat 105. Resiliently fitting the valve body 106 tothe valve stem 107 fixes the valve body 106 to the valve stem 107.Mounted around the outer face of the valve stem 107 is an O-ring 108that is in resilient contact with the inner face of the valve body 106.

One end of the valve stem 107 is supported in the regulator body 38A inan axially movable manner by an O-ring 109 disposed between the valvestem 107 and the inner face of the third hole 97 c of the mounting hole97. The outer face of the valve body 106 is in sliding contact with theinner face of the valve seat member 98 at a plurality of points that arespaced at equal intervals in the circumferential direction. Flowpassages 110 are formed between adjacent sliding contact parts, the flowpassages 110 extending along the axial direction of the valve stem 107between the valve body 106 and the valve seat member 98.

A retaining plate 111 is provided so as to be in contact with the stepformed between the second and third holes 97 b and 97 c. The retainingplate 111 is for retaining the O-ring 109 on the step between the thirdand fourth holes 97 c and 97 d of the mounting hole 97. Disposed betweenthe retaining plate 111 and the valve body 106 is a spring 112 exertinga spring force in a direction that seats the valve body 106 on the valveseat 105.

A spring chamber 115 is formed between the cover 91 and the diaphragm93. Housed in the spring chamber 115 is a coil spring 116 biasing thediaphragm 93 toward the pressure-reducing chamber 94 side.

Provided within the cylindrical part 91 a of the cover 91 is a housinghole 117 extending coaxially with the valve hole 104 and having anaperture at its outer end. The housing hole 117 is formed from athreaded hole part 117 a that is toward the outside in the axialdirection and a slide bore part 117 b that is toward the inside in theaxial direction, has a larger diameter than that of the threaded holepart 117 a and is coaxially connected to the threaded hole part 117 a.

The surface of the central part of the diaphragm 93 facing thepressure-reducing chamber 94 side is in contact with a first diaphragmretainer 118 having an integral cylindrical part 118 a penetrating thecentral part of the diaphragm 93 and projecting toward the springchamber 115 side. The surface of the central part of the diaphragm 93facing the spring chamber 115 side is in contact with a second diaphragmretainer 120 whose inner periphery is engaged with an annular step 119provided on the outer face of the cylindrical part 118 a, the centralpart of the diaphragm 93 thereby being interposed between the seconddiaphragm retainer 120 and the first diaphragm retainer 118.

A diaphragm rod 121 is coaxially joined to the other end of the valvestem 107, that is to say, the end on the diaphragm 93 side. Thediaphragm rod 121 is inserted into the central part of the firstdiaphragm retainer 118 from the pressure-reducing chamber 94 side.Provided on the inner face of the cylindrical part 118 a in the firstdiaphragm retainer 118 is an annular step 122 facing thepressure-reducing chamber 94 side. The diaphragm rod 121 engages withthe annular step 122. The second diaphragm retainer 120 is interposedbetween the diaphragm 93 and an auxiliary retainer 123. A nut 125 isscrewed around a threaded shaft part 121 a of the diaphragm rod 121 withwashers 124 disposed between the nut 125 and the auxiliary retainer 123,the threaded shaft part 121 a projecting out of the cylindrical part 118a. Tightening the nut 125 clamps the central part of the diaphragm 93between the two diaphragm retainers 118 and 120 and also fixes the valvestem 107 to the central part of the diaphragm 93. Moreover, in order toseal the gap between the pressure-reducing chamber 94 and the springchamber 115, an O-ring 126 is mounted around the outer periphery of thediaphragm rod 121 so as to be in a resilient contact with the inner faceof the cylindrical part 118 a.

With regard to the diaphragm 93, a part connected to the valve stem 107,that is to say, its central part, and a part interposed between theregulator body 38A and the cover 91, that is to say, its periphery, arecomparatively thick, and a part connecting the central part and theperiphery is formed into a comparatively thin curved shape. Inaccordance with the diaphragm 93 having such an arrangement, thepressure resistance of the diaphragm 93 can be increased and itsresponsiveness at low temperature can be improved.

The second diaphragm retainer 120 is integrally provided on its outerperipheral side with a flexure-restricting part 120 a for restrictingflexure of the diaphragm 93 toward the spring chamber 115 side. Theflexure-restricting part 120 a is formed in a curved shape protrudingtoward the spring chamber 115 side. The outer edge of theflexure-restricting part 120 a is positioned so as to face the innerface of the cover 91 at a close distance. The thickness of the part ofthe diaphragm 93 corresponding to the gap between the outer edge of theflexure-restricting part 120 a and the inner periphery of the cover 91is made greater than the above-mentioned gap.

Since the second diaphragm retainer 120 has the above-mentioned shape,even when a pressure higher than a preset level is applied to thepressure-reducing chamber 94, the diaphragm 93 can be curved smoothlyalong the second diaphragm retainer 120 toward the inner face of thecover 91, thereby preventing the diaphragm 93 from bending toward thespring chamber 115 at the outer edge of the second diaphragm retainer120, preventing reduction of the life-span of the diaphragm 93 due tothe bending, and increasing the durability of the diaphragm 93.

An adjustment screw 127 is screwed into the aperture at the outer end ofthe housing hole 117, that is to say, the threaded hole part 117 a, inan axially movable manner. A lock nut 128 is screwed around a part ofthe adjustment screw 127 projecting out of the cover 91, the lock nut128 regulating the axial position of the adjustment screw 127. Theadjustment screw 127 is also provided with an open hole 129 for openingthe spring chamber 115 to the air.

The coil spring 116 is provided in compression between the adjustmentscrew 127 and a leaf spring 132 that is in contact with the auxiliaryretainer 123 mounted on the diaphragm 93 on the spring chamber 115 side.Adjusting the axial position of the adjustment screw 127 can therebyadjust the spring load of the coil spring 116.

Referring also to FIGS. 10 and 11, the leaf spring 132 is in frictionalcontact with the inner face of the cylindrical part 91 a, which is apart of the valve housing 90, thereby applying a sliding resistance tothe diaphragm 93. The leaf spring 132 is formed from a bottomedcylindrical cup 132 a and a plurality of leaves 132 b connectedintegrally with the open end of the cup 132 a so as to be in resilientsliding contact with the inner face of the slide bore part 117 b of thecylindrical part 91 a at a plurality of, for example, eight pointsspaced at equal intervals in the circumferential direction. The closedend of the cup 132 a is interposed between the coil spring 116 and theauxiliary retainer 123 mounted on the central part of the diaphragm 93on the spring chamber 115 side.

A plurality of, for example, two exit passages 133 parallel to themounting hole 97 are provided in the regulator body 38A, one end of eachof the exit passages 133 communicating with the pressure-reducingchamber 94. The other ends of the exit passages 133 open in common in aconnecting hole 134 provided in the projection 51 a placed on the secondend face 51 side of the regulator body 38A.

In the primary pressure-reducing valve 41 having the above-mentionedarrangement, when high pressure CNG does not flow into the valve chamber103, the diaphragm 93 bends toward the pressure-reducing chamber 94 sidedue to the spring force of the coil spring 116, and the valve body 106is detached from the valve seat 105, thereby opening the valve hole 104.When high pressure CNG flows into the valve chamber 103 and further tothe pressure-reducing chamber 94 side via the valve hole 104, and thepressure of the pressure-reducing chamber 94 accordingly increases tosuch a degree that the diaphragm 93 bends toward the spring chamber 115side against the spring force of the coil spring 116, the valve body 106becomes seated on the valve seat 105 thereby blocking the valve hole104. Repeating the above-mentioned opening and blocking of the valvehole 104 reduces the pressure of the CNG that has flowed in the valvechamber 103 at high pressure, for example, 25 to 1 MPa to, for example,0.6 to 0.7 MPa and supplies it from the pressure-reducing chamber 94 tothe exit passages 133.

Referring in particular to FIG. 6, a bottomed mounting hole 135 isprovided in the projection 51 a of the regulator body 38A. The pressureswitch 42 is screwed into the mounting hole 135. A detector hole 136 isprovided in the regulator body 38A coaxially with the mounting hole 97,the detector hole 136 opening on the inner face of the mounting hole 135at the closed end side. Also provided in the regulator body 38A is acommunicating hole 137 providing communication between the connectinghole 134 and the detector hole 136. The pressure switch 42 changes itsswitching mode according to whether the pressure of the CNG whosepressure has been reduced by the primary pressure-reducing valve 41 andthat is en route from the exit passages 133 to the connecting hole 134becomes equal to or exceeds, for example, 1.65 MPa.

The secondary pressure-reducing valve 31 is connected to the connectinghole 134 of the regulator RA, and its arrangement is explained below.

(Secondary Pressure-reducing Valve 31)

Referring to FIGS. 12 to 16 together, a valve housing 140 for thesecondary pressure-reducing valve 31 is formed by fastening, by means ofa plurality of bolts 144, a body 141 to a cover 143 with a partition 142disposed therebetween. Opposite ends of each of a plurality of dowelpins 145 penetrating the partition 142 are fitted in the body 141 andthe cover 143 respectively, thereby positioning the body 141, thepartition 142 and the cover 143 relative to each other.

The periphery of the partition 142 is interposed between the body 141and the cover 143, and the periphery of a diaphragm 146 is interposedbetween the partition 142 and the cover 143. A pressure-reducing chamber147 is formed between the body 141 and the partition 142, a pressureaction chamber 148 is formed between the partition 142 and one face ofthe diaphragm 146, the pressure action chamber 148 communicating withthe pressure-reducing chamber 147, and a spring chamber 149 is formedbetween the other face of the diaphragm 146 and the cover 143.

Referring also to FIG. 17, provided on the body 141 are a recess 150opening so as to face the partition 142 side so that the above-mentionedpressure-reducing chamber 147 is formed between the recess 150 and thepartition 142, and a bottomed mounting hole 151, one end thereof openingat the central part of the closed end of the recess 150 and the otherend being closed. Moreover, provided at the closed end of the mountinghole 151 is a boss 152 protruding toward the pressure-reducing chamber147 side.

A female thread 153 is cut into the inner face of the mounting hole 151on the pressure-reducing chamber 147 side. A cylindrical valve seatmember 154 is screwed into the female thread 153. Fitted on the outerface of the valve seat member 154 is an O-ring 155 that is in resilientcontact with the inner face of the mounting hole 151.

Projectingly provided on the end face of the valve seat member 154 onthe pressure-reducing chamber 147 side are a plurality of, for example,four projections 157. The projections 157 form therebetween a pluralityof, for example, four channels 156 extending in the radial direction ofthe seat valve member 153 in a plane perpendicular to the axis of themounting hole 151, the channels 156 being arranged in a cross shape.When the valve seat member 154 is screwed into the female thread 153,the valve seat member 154 can therefore be rotated by engaging a tool(not illustrated) with the channels 156 arranged in the cross shape,thereby easily mounting the valve seat member 154 in the body 141.

A valve chamber 158 is formed between the valve seat member 154 and theclosed end of the mounting hole 151, the valve chamber 158 communicatingwith an input port 159 provided in the body 141 so as to open on a sideface of the body 141. CNG is introduced from the primarypressure-reducing valve 41 into the input port 159, that is to say, thevalve chamber 158.

The body 141 is provided with an output port 160 opening on a sidedifferent from that provided with the input port 159, and a passage 161providing communication between the output port 160 and thepressure-reducing chamber 147. CNG is guided from the pressure-reducingchamber 147 to the gaseous fuel pipeline 36 via the passage 161 and theoutput port 160.

The valve seat member 154 is integrally provided with an inward collar154 a protruding inward in the radial direction at the end on thepressure-reducing chamber 147 side. A valve hole 162 is formed on theinner periphery of the inward collar 154 a so as to communicate with thepressure-reducing chamber 147. Formed on the inner periphery of theinner collar 154 a so as to project toward the valve chamber 158 side isan annular valve seat 163 facing the valve chamber 158. The valve hole162 opens at the central part of the valve seat 163.

Provided on the boss 152 coaxially with the valve hole 162 is a bottomedslide bore 164 opening on the valve hole 162 side. A valve body 165 isslidably fitted in the slide bore 164. Attached to the valve body 165 isan annular rubber seal 166 that can be seated on the valve seat 163.

The valve body 165 is provided with a through hole 167 having a femalethread 167 a on at least on a part thereof on the pressure-reducingchamber 147 side, the through hole 167 extending between the oppositeends of the valve body 165 in the axial direction. Screwed into thefemale thread 167 a is one end of a valve stem 168 that is coaxial withthe valve hole 162. That is to say, the valve body 165 is fixed to saidone end of the valve stem 168.

A back pressure chamber 169 is formed between the valve body 165 and theclosed end of the slide bore 164. Mounted on the outer face of the valvebody 165 is an O-ring 170 that is in resilient sliding contact with theinner face of the slide bore 164.

Referring to FIGS. 18 and 19 together, the partition 142 is formed in adish shape having a circular recess 171 facing the diaphragm 146 side soas to form the pressure action chamber 148 between the partition 142 andthe diaphragm 146. An annular channel 172 is provided on the partition142 so as to surround the recess 171. Fitted in the annular channel 172is a ring-shaped outer peripheral seal part 146 a of the peripheral edgeof the diaphragm 146.

Provided in the partition 142 is a through hole 173 allowing the valvestem 168 to penetrate the central part of the partition 142 in anaxially movable manner. In addition, a plurality of, for example, fourrestricting projections 174 are arranged on the partition 142 so as tosurround the through hole 173 and project toward the diaphragm 146 side.The restricting projections 174 restrict the stroke limit of thediaphragm 146 in the direction which reduces the volume of the pressureaction chamber 148.

Furthermore, formed in the partition 142 is a communicating hole 175 forproviding communication between the pressure action chamber 148 and thepressure-reducing chamber 147.

In FIG. 20, the diaphragm 146 is formed integrally from the ring-shapedouter peripheral seal part 146 a, a cylindrical valve stem-connectingpart 146 b and a flexural part 146 c having a transverse cross sectionthat protrudes toward the spring chamber 149 side and being disposedinward relative to the outer peripheral seal part 146 a. The outerperipheral seal part 146 a is fitted in the annular channel 172 of thepartition 142 and is interposed between the partition 142 and the cover143. The cylindrical valve stem-connecting part 146 b is disposed in thecenter for connecting to the valve stem 168. The diaphragm 146 is formedso that, in a natural state where no external force is applied thereto,the inner periphery of the flexural part 146 c is offset toward thepressure-reducing chamber 147 side by a predetermined amount e relativeto the outer periphery of the flexural part 146 c.

A first diaphragm retainer 176 is in contact with the surface of thediaphragm 146 facing the pressure action chamber 148 between theflexural part 146 c and the valve stem-connecting part 146 b. A seconddiaphragm retainer 178 having in its central part an insertion hole 177is in contact with the surface of the diaphragm 146 facing the springchamber 149 inside the flexural part 146 c so that the diaphragm 146 isinterposed between the first diaphragm retainer 176 and the seconddiaphragm retainer 178.

The valve body 165 is fixed to one end of the valve stem 168; the otherend of the valve stem 168 coaxially penetrates the valve hole 162 of thevalve seat member 154, the through hole 173 of the partition 142, thevalve stem-connecting part 146 b of the diaphragm 146, and the centralparts of the first and second diaphragm retainers 176 and 178 and,extends toward the spring chamber 149 side. The valve stem 168 isprovided with an annular step 179 and an annular step 180. The annularstep 179 engages with the inner peripheral edge of the first diaphragmretainer 176. The valve stem-connecting part 146 b is interposed betweenthe annular step 180 and the second diaphragm retainer 178. Mountedaround the outer periphery of the valve stem 168 is an O-ring 199 thatis in resilient contact with the inner face of the through hole 173.

Said other end of the valve stem 168 penetrates the valvestem-connecting part 146 b of the diaphragm 146 and the insertion hole177 of the second diaphragm retainer 178, projects into the springchamber 149 and forms a threaded shaft part 168 a. A nut 182 is screwedaround the threaded shaft part 168 a with a washer 181 disposed betweenthe second diaphragm retainer 178 and the nut 182. Tightening the nut182 clamps the central part of the diaphragm 146 between the first andsecond diaphragm retainers 176 and 178, and connects the valve stem 168to the central part of the diaphragm 146. Moreover, provided on thevalve stem 168 is a communicating passage 183 providing communicationbetween the pressure-reducing chamber 149 and the back pressure chamber169 via the through hole 167 of the valve body 165.

The diaphragm 146 whose central part is clamped between the twodiaphragm retainers 176 and 178, the valve stem 168 connected to thecentral part of the diaphragm 146, and the valve body 165 fixed to thevalve stem 168 are assembled to the valve housing 140 so that, when thediaphragm 146 is in its natural state without any external force actingon it, the rubber seal 166 of the valve body 165 is detached from thevalve seat 163.

The cover 143 has a cylindrical part 143 a provided with an end wall 143b at the end opposite the diaphragm 146. Integrally provided so as to beconnected to the central part of the end wall 143 b is a support tube184 arranged coaxially within the cylindrical part 143 a and open atboth its ends.

The support tube 184 is provided coaxially with a small diameter hole185 on the axially inner side and a large diameter hole 186 on theaxially outer side, a female thread 187 being cut into at least one partof the large diameter hole 186. Screwed into the support tube 184 is anadjustment screw 188 whose axial position can be adjusted. Theadjustment screw 188 is formed by coaxially connecting a small diametershaft part 188 a and a large diameter shaft part 188 b. The smalldiameter shaft part 188 a is fitted in the small diameter hole 185.Mounted on the outer face of the small diameter shaft part 188 a is anannular seal 189 that is in resilient contact with the inner face of thesmall diameter hole 185. The large diameter shaft part 188 b has on itsouter periphery a male thread 190 that mates with the female thread 187.Provided on the outer end of the large diameter shaft part 188 b is anengagement recess 191 that can engage with a rotating tool. The axialposition of the adjustment screw 188 is set so that the inner end of thesmall diameter shaft part 188 a enters the spring chamber 149 and theouter end of the large diameter shaft part 188 b is positioned inwardrelative to the outer face of the end wall 143 b.

Setting the axial position of the adjustment screw 188 in this way formsa recess 192 in the outer end part of the large diameter hole 186, therecess 192 employing the outer end of the large diameter shaft part 188b as its closed end. The recess 192 is filled with a filler 193 that canbe solidified. Moreover, a seal 194 is bonded to the outer face of theend wall 143 b to thereby cover the recess 192.

The female thread 187 with which the adjustment screw 188 mates is cutinto the large diameter hole 186 so that at least one part of the femalethread 187 faces the recess 192.

A retainer 195 is in contact with and supported on the inner end of theadjustment screw 188 within the spring chamber 149. A coil spring 196 isprovided in compression between the retainer 195 and a leaf spring 197that is in contact with the second diaphragm retainer 178 mounted in thecentral part of the diaphragm 146 on the spring chamber 149 side. Thecoil spring 196 biases the diaphragm 146 so that the valve body 165departs from the valve seat 163. Adjusting the axial position of theadjustment screw 180 can therefore adjust the spring load of the coilspring 196.

Referring to FIGS. 21 and 22 together, the leaf spring 197 is infrictional contact with the inner face of the cylindrical part 143 a,which is a part of the valve housing 140, thereby applying slidingresistance to the diaphragm 146. The leaf spring 197 is formed from abottomed cylindrical cup 197 a and a plurality of leaves 197 bintegrally connected to the open end of the cup 197 a so as to be inresilient sliding contact with a plurality of, for example, five pointsspaced at equal intervals in the circumferential direction on the innerface of the cylindrical part 143 a. The closed end of the cup 197 a isinterposed between the coil spring 196 and the second diaphragm retainer178 mounted in the central part of the diaphragm 146 on the springchamber 149 side.

Furthermore, a connecting tube 198 is connected to the cover 143. Thenegative intake pressure of the engine E is introduced into the springchamber 149 via the connecting tube 198 and a pipeline (not illustrated)connected to the connecting tube 198.

In the secondary pressure-reducing valve 31 having the above-mentionedarrangement, when no CNG flows into the valve chamber 158, the diaphragm146 bends toward the pressure-reducing chamber 147 due to the springforce of the coil spring 196, thereby detaching the valve body 165 fromthe valve seat 163 so as to open the valve hole 162. When CNG flows intothe valve chamber 158, then to the pressure-reducing chamber 147 via thevalve hole 162 and further to the pressure action chamber 148, and thedifference in pressure between the pressure action chamber 148 and thespring chamber 149 increases to such a degree that the diaphragm 146bends toward the spring chamber 149 side against the spring force of thecoil spring 196, the rubber seal 166 of the valve body 165 becomesseated on the valve seat 163, thereby blocking the valve hole 162.Repeating the above-mentioned opening and blocking of the valve hole 162reduces the pressure of the CNG that has flowed into the valve chamber158 at a pressure of, for example, 0.6 to 0.7 MPa to, for example, 0.2to 0.3 MPa and supplies it from the pressure-reducing chamber 147 to theinjectors 32 of the engine E via the output port 160 and the pipeline33.

The action of the first embodiment is explained below. Among the highpressure filter 39, the solenoid cut-off valve 40, the primarypressure-reducing valve 41, the pressure switch 42, and the secondarypressure-reducing valve 31, which are provided between the CNG tanks 20and the injectors 32 of the engine E, the high pressure filter 39, thesolenoid cut-off valve 40, and the primary pressure-reducing valve 41are disposed on the common regulator body 38A so as to form theregulator RA, the common regulator body 38A having the passage 59providing connection between the high pressure filter 39 and thesolenoid cut-off valve 40, the passage 80 providing connection betweenthe solenoid cut-off valve 40 and the primary pressure-reducing valve41, and the exit passages 133 having one end connected to the primarypressure-reducing valve 41, and the pressure switch 42 being attached tothe regulator RA.

Forming the regulator RA in this way by integrating on the regulatorbody 38A the high pressure filter 39, the solenoid cut-off valve 40 andthe primary pressure-reducing valve 41, which are on the high pressureside, simplifies the arrangement of the passages in the regulator body38A in comparison with an arrangement in which the whole of the highpressure section and the low pressure section are integrated to form aregulator, and it becomes correspondingly easier to machine theregulator body 38A. Moreover, the regulator RA can be made compact,thereby reducing restrictions on the layout relative to other componentswhen it is mounted on a vehicle V.

Furthermore, since the valve housing 140 of the secondarypressure-reducing valve 31, which is on the low pressure side, is formedseparately from the regulator body 38A, the valve housing 140 of thesecondary pressure-reducing valve 31 can be made of a material havingcomparatively low strength, thereby achieving a reduction in cost.

Furthermore, the primary pressure-reducing valve 41 includes the leafspring 132 that makes frictional contact with the slide bore part 117 bof the cylindrical part 91 a, which is a part of the valve housing 90,thereby applying sliding resistance to the diaphragm 93. The secondarypressure-reducing valve 31 includes the leaf spring 197 that makesfrictional contact with the inner face of the cylindrical part 143 a,which is a part of the valve housing 140, thereby applying slidingresistance to the diaphragm 146.

These leaf springs 132, 197 are formed from the bottomed cylindricalcups 132 a, 197 a respectively and the pluralities of leaves 132 b, 197b formed integrally with the open ends of the cups 132 a, 197 a so as tobe in resilient sliding contact with the inner faces of the cylindricalparts 91 a, 143 a at a plurality of points spaced at equal intervals inthe circumferential direction. The closed ends of the cups 132 a, 197 aare interposed between the coil springs 116, 119 and the retainers 123,178 mounted on the central part of the diaphragms 93, 146 on the springchamber 115, 149 side.

That is to say, the leaf springs 132, 197 apply sliding resistance tothe diaphragms 93, 146 against the self-induced vibration of the coilsprings 116, 196 as a result of the plurality of leaves 132 b, 197 bbeing in resilient sliding contact with the inner faces of thecylindrical parts 91 a, 143 a. Even when the diameters of thecylindrical parts 91 a, 143 a decrease as the diameters of thediaphragms 93, 146 decrease, the contact areas between the leaf springs132, 197 and the cylindrical parts 91 a, 143 a do not change. The levelsof sliding resistance exerted by the leaf springs 132, 197 therefore donot increase as the dimensions of the primary pressure-reducing valve 41and the secondary pressure-reducing valve 31 reduce. Furthermore, thelevels of sliding resistance due to the resilient sliding contactbetween the leaf springs 132, 197 and the cylindrical parts 91 a, 143 ado not change as the temperature changes. It is therefore possible toapply a stable sliding resistance against the selfinduced vibration ofthe coil springs 116, 196 regardless of a reduction in the dimensions ofthe diaphragms 93, 146 and a change in the temperature, therebypreventing any degradation in the responsiveness of the primarypressure-reducing valve 41 and the secondary pressure-reducing valve 31.

Moreover, since the plurality of leaves 132 b, 197 b are supported bythe cups 132 a, 197 a having a comparatively high rigidity, whenassembling the leaf springs 132, 197 to the valve housing 90, 140,breakage, etc. of the leaves 132 b, 197 b can be avoided, therebyenhancing the ease of assembly.

With regard to the secondary pressure-reducing valve 31, the peripheraledge of the diaphragm 146 is interposed between the cover 143 and thepartition 142 that is interposed between the cover 143 and the body 141,the pressure-reducing chamber 147 is formed between the partition 142and the body 141, and the pressure action chamber 148 is formed betweenthe partition 142 and one surface of the diaphragm 146, the pressureaction chamber 148 communicating with the pressure-reducing chamber 147.It is therefore possible to enhance the machining precision bysimplifying the structure of a part of the body 141 facing thepressure-reducing chamber 147, and machining the partition 142 caneasily be carried out in a state where it is separated from the body141.

Furthermore, although the diameter of the pressure action chamber 148changes as the diameter of the diaphragm 146 changes, the diameter ofthe pressure-reducing chamber 147 disposed between the partition 142 andthe pressure action chamber 148 can be determined independently of achange in the diameter of the diaphragm 146. Even when the diameter ofthe diaphragm 146 is made small in order to answer a need for reducingthe dimensions of the secondary pressure-reducing valve 31, it isunnecessary to decrease the diameter of the pressure-reducing chamber147, thereby avoiding the occurrence of any change in the flowcharacteristics that would cause the gas pressure of thepressure-reducing chamber 147 to fall below the target control pressureby a large amount.

Moreover, since the gas pressure of the pressure-reducing chamber 147does not act directly on said one surface of the diaphragm 146, it ispossible to prevent an excessive load from being imposed on thediaphragm 146 when the gas pressure of the pressure-reducing chamber 147changes by a large amount, thereby protecting the diaphragm 146.

Since the body 141 is provided with the slide bore 164 in which thevalve body 165 is a sliding fit, the axial movements of the valve body165 and the valve stem 168 are supported at the two points; on the innerface of the slide bore 164 of the body 141; and on the inner face of thethrough hole 173 provided on the partition 142, thereby preventing thevalve body 165 and the valve stem 168 from tilting and ensuring reliableopening and closing operations of the valve body 165.

In the secondary pressure-reducing valve 31, the diaphragm 146, thevalve stem 168 and the valve body 165 are assembled to the valve housing140 so that, when the diaphragm 146 is in its natural state without anyexternal force acting on it, the rubber seal 166 of the valve body 165is detached from the valve seat 162. When the diaphragm 146 bends so asto seat the valve body 165 on the valve seat 163 in response to theaction of the gas pressure of the pressure action chamber 148 thatcommunicates with the pressure-reducing chamber 147, the diaphragm 146bends toward the spring chamber 149 side so as to exert a resilientforce in the same direction as the direction of the spring force of thecoil spring 196, that is to say, opposite to the direction in which thegas pressure of the pressure-reducing chamber 147 closes the valve. Whenthe valve body 165 is detached from the valve seat 163 to a great extentso as to increase the gas flow, the resilient force exerted by thediaphragm 146, against the force of the gas pressure of thepressure-reducing chamber 147 in the direction that closes the valve,becomes small. It is thereby possible to minimize any adverse effect onthe responsiveness arising from the resilient force exerted by thediaphragm 146, and even when the gas flow increases the pressure of thepressure-reducing chamber 147 is not controlled at a lower value.

Moreover, the diaphragm 146 is formed integrally from the ring-shapedouter peripheral seal part 146 a clamped by the valve housing 140, thevalve stem-connecting part 146 b connected to the valve stem 168 and theflexural part 146 c having a transverse cross section that protrudestoward the spring chamber 149 side and is disposed inward relative tothe outer peripheral seal part 146 a. The diaphragm 146 is formed sothat in its natural state the inner periphery of the flexural part 146 cis offset toward the pressure-reducing chamber 147 side by thepredetermined amount e relative to the outer periphery of the flexuralpart 146 c. When the diaphragm 146 is assembled to the valve housing 140in its natural state, the inner periphery of the flexural part 146 c ofthe diaphragm 146, that is to say, the central part to which the valvebody 165 is connected via the valve stem 168, is offset toward thepressure-reducing chamber 147 side relative to the external periphery ofthe flexural part 146 c. It is easy to achieve a state in which, whenthe diaphragm 146 is assembled to the valve housing 140 in its naturalstate, the valve body 165 is detached from the valve seat 163, therebymaking the assembly operation of the diaphragm 146 easy.

Moreover, in the secondary pressure-reducing valve 31, the end wall 143b is provided at the end of the cylindrical part 143 a on the sideopposite to the diaphragm 146, the cylindrical part 143 a forming a partof the valve housing 140. The adjustment screw 188 is screwed into thesupport tube 184 arranged coaxially within the cylindrical part 143 a,which is integrally provided so as to be connected the end wall 143 b.The spring load of the coil spring 196 can be adjusted by the axialposition of the adjustment screw 188. Merely adjusting the axialposition of the adjustment screw 188 by screwing it into the supporttube 184 can adjust the spring load of the coil spring 196, therebyreducing the number of components required to adjust the spring load ofthe coil spring 196 as well as the number of assembly steps.

The support tube 184 is coaxially provided with the small diameter hole185 on the inward side and the large diameter hole 186 on the outwardside. The adjustment screw 188 is fitted into the small diameter hole185 and has on its tip side the small diameter shaft part 188 a on whoseouter face is mounted the annular seal 189, which is in resilientcontact with the inner face of the small diameter hole 185. It istherefore possible to minimize any damage to the seal 189 due to thefemale thread 187 provided on the inner face of the large diameter hole186 when the adjustment screw 188 is inserted into the support tube 184.

Since the adjustment screw 188 is screwed into the support tube 184until the outer end of the adjustment screw 188 reaches a position thatis inward relative to the outer face of the end wall 143 b, theadjustment screw 188 does not project out of the outer face of the endwall 143 b, thereby contributing to a reduction in the dimensions of thesecondary pressure-reducing valve 31.

Furthermore, since the recess 192 is formed in the outer end part of thelarge diameter hole 186, employs the outer end of the large diametershaft part 188 b of the adjustment screw 188 as its closed end, and isfilled with the filler 193, solidifying the filler 193 can gain theeffects of preventing the adjustment screw 188 from rotating and ofpreventing erroneous operation while requiring no lock nut nor cap. Inparticular, putting the filler 193 into the engagement recess 191 in theouter end part of the adjustment screw 188 can yet more reliably preventthe adjustment screw 188 from rotating.

Moreover, the female thread 187 into which the adjustment screw 188 isscrewed is formed in the large diameter hole 186 so that at least onepart of the female thread 187 faces the recess 192. The filler 193filling the recess 192 and entering the threads of the female thread 187can be reliably retained within the recess 192 and can also efficientlypenetrate into the part where the male thread 190 of the adjustmentscrew 188 and the female thread 187 of the large diameter hole 186 arescrewed together, thereby yet more reliably stopping the regulatingthread 188 from rotating.

FIGS. 23 and 24 illustrate a second embodiment of the present invention.Parts corresponding to those in the above-mentioned first embodiment aredenoted using the same reference numerals and symbols.

A high pressure filter 39, a solenoid cut-off valve 40 and a primarypressure-reducing valve 41 are disposed on a common regulator body 38Bto form a regulator RB.

A flat mounting face 201 is formed on an end face of the regulator body38B on the side opposite to the side where the primary pressure-reducingvalve 41 is disposed. Opening on the mounting face 201 is one end of anexit passage 133′ provided in the regulator body 38B, the other end ofthe exit passage 133′ communicating with a pressure-reducing chamber 94of the primary pressure-reducing valve 41.

Selectively mounted in a detachable manner on the mounting face 201 is abody 202A shown in FIG. 23 or a body 202B shown in FIG. 24. The bodies202A and 202B are each provided with a low pressure passage 203 thatcommunicates with the exit passage 133′ when the bodies 202A and 202Bare mounted on the mounting face 201.

Mounted on the body 202A shown in FIG. 23 is a relief valve 204, whichis safety means of a type different from the pressure switch 42. Therelief valve 204 is formed by housing a valve body 208 and a spring 209within a valve housing 208 that is fixed to the body 202A and that hasat its extremity a valve hole 205 communicating with the low pressurepassage 203, the valve body 208 having on its forward end a rubber seal207 capable of blocking the valve hole 205, and the spring 209spring-biasing the valve body 208 in the direction that blocks the valvehole 205 with the rubber seal 207. The valve housing 206 and the valvebody 208 are formed so that CNG flowing from the low pressure passage203 can be released to the outside when the valve hole 205 is open.

That is to say, the function of the relief valve 204 is to release CNGinto the air by opening the valve when the pressure of the low pressurepassage 203, that is to say, the output pressure of the primarypressure-reducing valve 41 becomes equal to or exceeds a set pressuredetermined by the spring 209, for example 1.65 MPa.

Mounted on the body 202B shown in FIG. 24 is a pressure switch 42 thatchanges its switching mode when the pressure of the low pressure passage203, that is to say, the output pressure of the primarypressure-reducing valve 41, becomes equal to or exceeds a presetpressure, for example 1.65 MPa, thereby outputting a signal to cut offthe solenoid cut-off valve 40.

In accordance with the second embodiment, in order to prevent a highpressure equal to or higher than the set pressure from being imposed onthe secondary pressure-reducing valve 31 (ref. the first embodiment), itis possible to freely choose the use of either the relief valve 204 forreleasing a part of the CNG output from the primary pressure-reducingvalve 41 when the output pressure of the primary pressure-reducing valve41 becomes equal to or exceeds the set pressure, or the pressure switch42 for cutting off the solenoid cut-off valve 40 when the outputpressure of the primary pressure-reducing valve 41 becomes equal to orexceeds the set pressure. It is thus possible to select either one ofthe relief valve 204 or the pressure switch 42 and connect it to theregulator RB, thereby enhancing the multi-purpose feature when thegaseous fuel supply system is mounted on a vehicle.

Although embodiments of the present invention have been explained above,the present invention is not limited by the above-mentioned embodiments,and the present invention can be modified in a variety of ways withoutdeparting from the spirit and scope of the appended claims.

What is claimed is:
 1. A vehicle gaseous fuel supply system comprising: a high pressure filter that removes impurities from a high pressure gaseous fuel supplied from a tank; a primary pressure-reducing valve that reduces the pressure of the gaseous fuel from which impurities have been removed by the high pressure filter; a solenoid cut-off valve disposed between the high pressure filter and the primary pressure-reducing valve; safety means that operates in response to the output pressure of the primary pressure-reducing valve becoming equal to or exceeding a set pressure; and a secondary pressure-reducing valve that further reduces the pressure of the gaseous fuel whose pressure has been reduced by the primary pressure-reducing valve and supplies it to an injector of an engine; wherein the high pressure filter, the solenoid cut-off valve, and the primary pressure-reducing valve are disposed on a common regulator body to form a regulator, the regulator body having a passage providing a connection between the high pressure filter and the solenoid cut-off valve, a passage providing a connection between the solenoid cut-off valve and the primary pressure-reducing valve, and an exit passage having one end connected to the primary pressure-reducing valve; and wherein, between the safety means and the secondary pressure-reducing valve which are connected to the other end of the exit passage, at least the secondary pressure-reducing valve has a valve housing formed as a body separate from the regulator body.
 2. The vehicle gaseous fuel supply system according to claim 1, wherein a mounting face for providing said other end of the exit passage with an opening is provided on the outer face of the regulator body, and bodies each having a low pressure passage and equipped with the safety means of different types operating in response to the pressure of the low pressure passage are selectively mounted in a detachable manner on the mounting face so that the low pressure passage communicates with said other end of the exit passage.
 3. The vehicle gaseous fuel supply system according to claim 2, wherein the plural types of safety means are a pressure switch that determines the cut-off timing of the solenoid cut-off valve and a relief valve. 